Vision disorders such as strabismus, amblyopia and refractive error are the leading causes of handicapping conditions in childhood. Over the past decade, there is an increasing amount of evidence that suggest that early diagnosis and treatment of these ocular disorders can result in beneficial outcomes. Indeed, early detection and treatment is critical because it can decrease the burden of visual impairment on the child, her/his family and the society at large. This has lead to widespread interest in screening programs. However, despite the wealth of knowledge regarding early treatment, very little evidence exists on the prevalence of vision disorders in children. Additionally, almost no evidence exists on minority populations. The primary objective of this study, the Multi-Ethnic Pediatric Eye Disease Study (MEPEDS) is to improve our understanding of the magnitude and causes of ocular disease problems in population based samples of African-American, Latino and Non-Hispanic White children in the United States. A population-based sample of three thousand children from each of the three ethnic/racial groups will undergo a comprehensive eye examination to determine the prevalence of refractive error, strabismus and amblyopia. MEPEDS will also be studying selected demographic, biological and behavioral risk factors associated with these diseases and the consequences of these diseases from a health related quality of life perspective.